The manufacture of film products such as X-ray photofilm necessitates extremely careful inspection to safeguard against the passage of sheets carrying any defects which can possibly be misinterpreted by radiologists as having a pathological significance after their exposure and development incident to patient diagnosis.
On the other hand, such products as X-ray film inevitably present anomalies in their manufacture which can only be perceived by supersensitive automatic scanning systems, and sometimes by human visual inspectors as well. Some of these anomalies are entirely acceptable, especially in limited number, any under these circumstances do not warrant rejection of the film sheet.
The present invention is an on-line inspection system which is entirely automatic, thereby totally dispensing with human inspectors, so that the inspection process is completely objective. Moreover, the inspection system of this invention is much more sensitive than human visual inspection of the moving web, so that it is capable of detecting anomalies which would otherwise be missed. At the same time, the system can process inspection data so rapidly that film sheet quality can be classified on-the-fly within the time it takes each sheet to clear the inspection station. In addition, the invention correlates feature detection to the limits of each preselected area of a product marketable sheet, thus facilitating the later separation of bad film sheets from good to thereby conserve the maximum area of product possible consistent with rigorous inspection capability.
Finally, the inspection system of this invention is "trainable", in the sense that is can be operated in the course of its inspection task to acquire successive sets of feature signals, thus making it possible to correlate these signals with known visual quality standards at a later time off-line in order to refine inspection acceptance limits, which are thereafter used to meet specified product quality standards.
An important advantage of this invention is that the enhanced inspection sensitivity afforded characterizes the web product to a degree hitherto unknown, thereby permitting greater understanding of the up-stream manufacturing process and the numerous factors which are responsible for the ultimate as-received state of the product web.